1. Field of the Invention
This invention relates generally to thermoplastic honeycomb material, and more particularly to honeycomb panels made from thermoplastic elastomeric materials having perforations in the walls of the honeycomb core and/or in the facing material attached to the ends of the core walls.
2. Brief Description of the Prior Art
Early honeycomb panels were made from rigid materials which were both strong and lightweight. These materials, however, were not resilient and would permanently deform if crushed. See for example, the U.S. Pat. Nos. to Barut 3,018,205, Eakin et al. 3,556,917, and Kennedy et al. 3,483,070.
Applications of honeycomb made from resilient materials include Holland 2,887,425, and Landi et al. Nos. 4,422,183 and 4,485,568. Resilient honeycomb is made from thermoplastic elastomeric strips that are intermittently bonded together at staggered intervals along the length of the strip. The thermoplastic materials used in the manufacture of the honeycomb core provide resiliency so that the honeycomb returns to its original shape following deformation. Resilient honeycomb is used for shock absorption and vibration dampening as well as lightweight insulation.
The resilient honeycomb of the prior art consisted of whole strips of intermittently bonded thermoplastic that were stretched open to create the core. If facings were used, they too were made from whole material, and bonded to the planar surface created by the wall edges of the honeycomb core. The benefits of perforating the core walls and/or facings had not been fully realized. Perforating the thermoplastic material changes the response characteristics of the material by increasing the resiliency of the honeycomb while decreasing the total weight. Perforated honeycomb is lighter in weight than non-perforated honeycomb. Additionally, where a perforated honeycomb core is used with non-perforated facing material, liquids or gases contained therewithin can be transferred between the cells.